The invention is based on a slaving and blocking device for transmitting a torque from a driving part to a driven part and for stopping the driven part at a torque engaging the driven part, and in particular on a spindle block for a hand power tool with a rotating tool bit.
A slaving and blocking device of this kind is used as a so-called spindle block or automatic spindle lock in hand power tools, especially power drills or power screwdrivers, so that upon engagement of the tool bit with a workpiece, if there is a simultaneous failure of the energy supply, the hand power tool can be rotated with the tool bit so that the tool bit can be disengaged from its engagement with the workpiece, and also so that a single-sleeve drill chuck can be clamped and released.
A known spindle block (German Patent Disclosure DE 101 48 872 A1) includes a slaving means, connected in a manner fixed against relative rotation to the driving gear wheel for the spindle that carries the tool bit, with three slaving claws, offset from one another by the same circumferential angle; one roller star wheel, connected to the spindle in a manner fixed against relative rotation, with three radially extending points of the star, offset from one another by the same circumferential angle in the circumferential direction; one clamping ring, concentric with the slaving means and the roller star wheel, which is fixed nonrotatably in the housing of the hand power tool; and six clamping rollers. The slaving means receives the roller star wheel in such a way that in the circumferential direction, the slaving claws and the points of the star are located in alternation one behind each other and spaced apart from one another. The six clamping rollers are each placed in the free space, defined on the outside by the inner annular face of the clamping ring, between the slaving claws and the points of the star. If the driving gear wheel is motor-driven, then—regardless of its direction of rotation—three of the six clamping rollers at a time are pressed by the slaving claws against contact faces, extending radially, of the points of the star, and the torque of the driving gear wheel is thus transmitted via the slaving means, the clamping rollers and the rotor star onto the spindle and thus onto the tool bit held in a tool bit receptacle on the spindle. Conversely, if a driving torque is exerted on the spindle by the tool bit, then because of the rotation of the roller star wheel relative to the slaving means, three at a time of the total of six clamping rollers are displaced—again regardless of the direction of rotation—against clamping faces embodied on the points of the star and clamp firmly against the inner annular face, forming a counterpart clamping face, of the clamping ring. The entire torque is output to the clamping ring that is firmly connected to the housing and is not transmitted to the slaving means.
In engineering terms, such a spindle block is the combination of a clutch with rotary play and a controlled free-wheel. Because of the rotary play in the clutch, a clicking noise occurs when the hand power tool is braked, since the roller star wheel constantly swings back and forth between clutch engagement and free-wheeling, and thus the rollers are constantly lifting from the slaving faces on the slaving claws and the contact faces on the roller star wheel and striking slaving faces and contact faces again. This clicking noise is mistakenly thought by many users to be a defect of the hand power tool.